Combined pressure-volume sensor and guide wire assembly
The invention relates to a sensor and guide wire assembly including a pressure sensor having a plurality of terminals, the sensor being mounted in the distal end region of a core wire. It also includes two to four electrodes for conductance measurement, also provided in the distal end region. Two electrodes are electrically insulated from each other.
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The present invention relates to a guide wire for combined and simultaneous pressure and volume measurements in intravascular applications.
BACKGROUND OF THE INVENTIONThe possibility of performing measurements of properties such as pressure, temperature, volume and flow within internal body organs has become increasingly important in for example diagnosis of heart diseases.
Sensor and guide wire assemblies are guide wires that have measurement sensors located at or near their distal tips. These devices are typically used in applications to measure internal properties of internal tissues and fluids such as blood pressure. Sensor and guide wire assemblies may be introduced directly into arteries, veins or other body organs either by themselves or through catheters that have been previously positioned within a patient. A sensor and guide wire assembly is disclosed in U.S. Pat. No. 6,142,958 and a pressure sensor and guide wire assembly for biological pressure measurements is disclosed in U.S. Pat. No. 6,167,763 which hereby are incorporated by reference. These sensor and guide wire assemblies typically have an outer diameter of 0.035 mm (0.014″).
To increase the diagnostic value for many type of heart diseases and blood vessel alterations such as arteriosclerosis, it would be desirable to combine the pressure measurement with volumetric measurements. In the case of diagnosis of heart diseases so called “Pressure/Volume loops”, PV-loops, are of particular interest. An established method of estimating the volume of internal cavities of body organs, for example the heart chamber, is by measuring the conductance.
Vessel compliance is also a measure of the status of a blood vessel, in that a soft vessel will be subject to some expansion upon an increased internal pressure, whereas a stiff vessel, indicating arteriosclerosis, would be subject to less expansion. It would be desirable to be able to measure such vessel compliance in a reliable way.
U.S. Pat. No. 6,112,115 disclose a method of producing PV-loops using a conductance catheter and a micro pressure catheter inserted in said conductance catheter. The usage of several different catheters adds complexity, and possibly discomfort for the patient.
In U.S. Pat. No. 5,902,248 (Millar) the inventors describe a catheter tip pressure transducer also including electrodes enabling conductance measurements. However, a catheter lacks the flexibility of sensor and guide wire assemblies and thus less suitable for some applications requiring a very flexible distal region. Furthermore, this patent is directed to use in animals, in particular mice.
In order to create a minimal invasive method of diagnosis it is highly desirable to also include the ability for conductance measurements in the sensor and guide wire assembly.
SUMMARY OF THE INVENTIONThus, there exists a need for a sensor and guide wire assembly that also has the possibility of conductance measurements.
An object of the invention is therefore to provide a sensor and guide wire assembly having electrodes for enabling conductance measurements in a way that does not significantly increase the size and complexity of the assembly. This is achieved by the sensor and guide wire assembly defined in claim 1.
One advantage with such a sensor and guide wire assembly is that pressure and volume measurements can be done simultaneously with the same measurement device.
Another advantage is that the proposed sensor and guide wire assembly is equipped with the ability of conductance measurement without significantly increasing the outer diameter of the guide wire.
Still a further advantage is that the proposed combined pressure and volume guide wire assembly has a minimum complex construction and thus reducing manufacturing cost as well as reducing the risks of malfunction.
An additional advantage with the device according to the invention is that it is steerable to a desired location in the vascular system.
In one aspect of the invention the device and method is used to obtain the previously mentioned PV-loops.
In a further aspect, the device and method is used for determining vessel compliance, as discussed above, by performing pressure and conductance measurements in blood vessel.
Embodiments of the invention will now be described with reference to the figures.
With references to
The distal tip illustrated in
Shown in
For certain applications and in order to effect the electrical properties of the conductance measurement it can be of advantage to not use the entire distal tip 104 and the second coil 110 as the first electrode. Therefore, in an alternative embodiment, part of the distal tip and the second coil is covered with an insulating layer. The insulating layer is arranged to give the electrode, i.e. the uncovered part of the distal tip 104 and the second coil 110, the required dimensions and position. The dimensions could preferably be that of the other electrodes and the position determined by the above considerations. The chosen position could for example be at the distal end of the assembly or at the proximal end of the second coil 110.
In a further embodiment, one of the terminals of the sensor and one of the conductance electrodes can be connected to one and the same electrical lead (signal ground), which eliminates one electrical lead, thereby further simplifying the design.
A further simplification, according to another embodiment of the invention, is shown in
An advantageous feature of the assembly is the use of the proximal tub 112 as one electrical lead, and to use the tube at the very proximal end as one of the contact members 306 of the male connector. This is achieved by simply removing the insulating layer at the distal end to form a preferably circular segment, around the circumference of the tube.
Furthermore, since the core wire 102 is usable as one of the electrical leads, it can also be used for the purpose of providing another contact member 308 of the male connector.
According to one embodiment the electrodes are electrically isolated from each other and the first coil 100 by moulding the electrodes into a plastic material. Alternatively the first coil 100 can be made, at least party, of an insulating material or replaced by a tubular construction of insulating material.
In
The device disclosed above is usable in an inventive way to obtain necessary information to enable characterization of the status of the vascular system of a patient.
Thereby the method comprises introducing a sensor and guide wire assembly into the vascular system, locating it at the desired point of measurement by virtue of the steerablity of the device.
The assembly comprises a pressure sensor and conductance electrodes, preferably four. The assembly is suitably energized and the conductance response to pressure variations is detected in parallel with detection of said pressure variations.
These variations can then be used to calculate e.g. PV loops for the diagnosing of the condition of the heart, or for a calculation of the compliance of a blood vessel, e.g. to determine whether or not arteriosclerosis is at hand.
Additional advantages and modifications will readily be appreciated by those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, and representative devices, shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims.
Claims
1. A sensor and guide wire assembly having a distal end and a proximal end comprising:
- a core wire having a distal end and a proximal end;
- a sensor mounted in the distal end region of said core wire;
- a tube enclosing said core wire over at least a fraction of a length of said core wire such that said core wire extends out from a distal end of said tube;
- a first enclosure arranged to enclose a first portion of said core wire extending out from said distal end of said tube, said first enclosure being located nearer to said proximal end of said core wire than said sensor;
- a second enclosure arranged to enclose a second portion of said core wire extending out from said distal end of said tube, said second enclosure being located nearer to said distal end of said core wire than said sensor; wherein
- said guide wire further comprises at least two electrodes for conductance measurement, and said at least two electrodes are electrically insulated from each other.
2. Sensor and guide wire assembly according to claim 1, wherein said first enclosure is a first coil and said second enclosure is a second coil.
3. Sensor and guide wire assembly according to claim 2, wherein said second coil or a portion thereof is used as a first of said at least two electrodes.
4. Sensor and guide wire assembly according to claim 1, wherein said first of said at least two electrodes utilises said core wire as electrical connection to the proximal end of the guide wire.
5. Sensor and guide wire assembly according to claim 1, wherein the number of electrodes for conductance measurement is four.
6. Sensor and guide wire assembly according to claim 1, wherein at least one, and preferably two of said electrodes are cylindrical and enclose said guide wire.
7. Sensor and guide wire assembly according to claim 1, wherein said tube is made of electrically conducting material and for a larger first portion covered with an insulating material; and
- said conducting material of said tube is exposed over a smaller second portion and is utilised as the second of said at least two electrodes.
8. Sensor and guide wire assembly according to claim 7, wherein said second of said at least two electrodes utilises said first portion of said tube as electrical connection to the proximal end of the guide wire.
9. Sensor and guide wire assembly according to claim 1, wherein said sensor is a pressure sensor.
10. A sensor and guide wire assembly comprising:
- a pressure sensor having a plurality of terminals, the sensor being mounted in a distal end region of said guide wire;
- at least two electrodes for conductance measurement provided in the distal end region of said guide wire and wherein said at least two electrodes are electrically insulated from each other; wherein one of said sensor terminals and one of said conductance electrodes are connected to a common electrical lead.
11. Sensor and guide wire assembly according to claim 10, wherein the number of electrodes for conductance measurement is four.
12. A sensor and guide wire assembly comprising:
- a pressure sensor having a plurality of terminals, the sensor being mounted in a distal end region of said guide wire;
- at least two electrodes for conductance measurement provided in the distal end region of said guide wire and said at least two electrodes are electrically insulated from each other; and
- wherein the guide wire includes:
- a core wire having a distal end and a proximal end; and
- a tube enclosing said core wire over at least a fraction of a length of said core wire such that said core wire extends out from a distal end of said tube, and said core wire and said tube respectively being used as electrical leads.
13. Sensor and guide wire assembly according to claim 12, wherein the number of electrodes for conductance measurement is four.
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- Trinity College, The Biomedical Engineering Handbook, CRC Press, Inc., 1995, p. 488.
Type: Grant
Filed: Apr 19, 2002
Date of Patent: Aug 9, 2005
Patent Publication Number: 20040116816
Assignee: Radi Medical Systems AB (Uppsala)
Inventors: Lars Tenerz (Uppsala), Leif Smith (Uppsala), Ola Hammarström (Lerdala), Lars-Åke Brodin (Täby), Håkan Elmqvist (Bromma), Emil Söderqvist (Tumba), Camilla Carlsson (Älvsjö )
Primary Examiner: Robert L. Nasser
Attorney: Foley & Lardner LLP
Application Number: 10/475,126